This invention relates to ventilators for use in connection with openable windows and other glazing panels, the ventilators being of the type which can be used to provide a degree of ventilation when the openable window is in the closed position. This type of ventilation is usually now referred to as "secondary ventilation". It is particularly important in areas where external temperatures may be low or external weather inclement for use to provide ventilation for dwellings and other accommodation where the high performance seal of modern windows might otherwise give rise to environmental problems such as condensation within the dwelling or accommodation.